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Description

Many years ago I was a student studying electronics at MtSAC in Walnut, CA. While taking a class on AC theory and practice we were learning about how to draw Lissajou Curves in the XY mode of an oscilloscope. Lissajou Curves are draw by by using two function generators running a different frequencies to plot a circular pattern on the oscilloscope screen. My professor [Harry Smith], in a moment of jest, suggested that we would know that we were really good if we could write our name on the oscilloscope screens. The next year while studying microprocessors and DAC's (Digital to Analog Converters) I figured out how to write my name in the XY mode of the oscilloscope. Though conceptually I understood how to do it, I never did it.

Fast forward many years and I found myself teaching the microcontroller class at MtSAC. I thought it would be great to make a lab to the effect above (certainly more fun than just measuring the output of a DAC with a volt meter).

Details

All of the images shown on the analog oscilloscopes were created by students that took the class.

A link to the lab and source code is given. The lab is taught using a chipKIT Fubarino SD prototyping board.

With the source code you can find a Microsoft Excel file that can be used to generate source code to draw pictures. Fill in the grid with 1's where you want to generate code for the specific pixel.

Nice. There used to be a digital logic design class at Georgia Tech that did something like this. You'd build a TTL logic circuit to connect to a driver board. The board would send you 4 bits of a counter and you'd output 4 bits of X, 4 bits of Y, and a pen-up/down bit. Every quarter they'd change what you had to draw. You'd be graded on quality of the drawing and the cost of your circuit. It was a lot of tweaking your drawing points and order and checking Karnaugh maps.

Jacob: Awesome. Always wanted to see how sophisticated one could get with vector-images on my old 'scope. Nice work. And cool you turned it into a lab for students.
Adam, nothing *near* this level of sophistication, but I've done circles, "triangles," and four-leaf clovers using a laser reflecting off two woofers with mirrors-attached. Galvos wouldn't have quite the momentum-issue that prevented anything more sophisticated.

I look at a scope and see a black and white TV. I've always challenge my students to try and read a video stream off of an SD card and use the scope as a video display. I wish I had more time to do such fun nonsense.

Holy cow - I've seen images on scopes before, but you've taken it to the next level. I realize these are raster images, but I'm still wondering if they would translate to a laser display with galvos... hmmmm.

I've never used a galvo, what makes the images work on the scope is that the dwell time for any given pixel is large compared to the time it takes to deflect the beam. If you look at the picture of the piece sign you can see the scope traces as they move from pixel to pixel. The beam intensity of the scope can be lowered and this is why you cannot see these traces on all images. Some older scopes have a z-axis input that allows you to adjust the beam intensity from an external source. So maybe if you could turn the laser off between galvo moves then maybe your could achieve a similar effect.